I need your help on math...

I am trying to solve these questions but I can’t. I have to find the answers until tommorow. Do you know how to solve it? Any help will be appreciated!

1. Find the smallest distance between the start of the pivots and the surface. z=xy+5.
(As a note there is written √(x*x)(y*y)(z*z) )

2. Find this area on the surface 2x+3y+z-11=0 which minimizes the quantity Q=4*(x*x)(y*y)(z*z)
(There is a note <Langrad>)

3. Find the mass which is under the surface z=1/(y+2) and over the surface bounded by the curves y=x and (y*y)+x=2

4. Find the integral ∫∫∫vV dt
on (x*x)+(y*y)<=4
0<=z<=5
where V=((x*x)+(y*y))^(½)) * (x*Ix+y*Iy)